Defects in the subsystems of a xerographic, electrophotographic or similar image forming system, such as a laser printer, digital copier or the like, may give rise to visible streaks in a printed image. Streaks are primarily one-dimensional defects in an image that run parallel to the process (or slow scan) direction. In a printing system, an image input module is used to measure reflection from an image bearing surface and from test patches on the image bearing surface. Often, these image input modules are referred to as densitometers, as they are imaging the image bearing surface to detect the toner deposition or lack thereof on the image bearing surface. These measured reflections are used in a streak correction methodology in the printer.
In prior systems, the image input module uses a fluorescent lamp or a rare gas lamp for illuminating the image bearing surface and the test patches. The fluorescent lamp or the rare gas lamp used for illumination is a continuous source of light in the cross-process (or fast scan) direction. However, the fluorescent lamp or the rare gas lamp is relatively expensive.